
local set_node = minetest.set_node
local get_node = minetest.get_node
local swap_node = minetest.swap_node
local ipairs = ipairs
local math_random = math.random



-- Content IDs used with the voxel manipulator.
local c_air             = minetest.get_content_id("air")
local c_ignore          = minetest.get_content_id("ignore")
local c_stone           = minetest.get_content_id("default:stone")

-- These 2 types are placed at and below the level of the brimstone ocean.
-- They disallow the C++ cavegen from running.
local c_redrack         = minetest.get_content_id("rackstone:redrack")
local c_rackstone       = minetest.get_content_id("rackstone:rackstone")

-- These 2 types are placed above the brimstone ocean.
-- The C++ cavegen is allowed to run in these nodes.
local c_mgredrack       = minetest.get_content_id("rackstone:mg_redrack")
local c_mgrackstone     = minetest.get_content_id("rackstone:mg_rackstone")

local c_whitestone      = minetest.get_content_id("whitestone:stone")
local c_mossycobble     = minetest.get_content_id("default:mossycobble")
local c_cobble          = minetest.get_content_id("default:cobble")
local c_netherbrick     = minetest.get_content_id("rackstone:brick")
local c_cobblestair     = minetest.get_content_id("stairs:stair_cobble")
local c_netherstair     = minetest.get_content_id("stairs:stair_rackstone_brick")
local c_water           = minetest.get_content_id("default:water_source")
local c_waterflow       = minetest.get_content_id("default:water_flowing")
local c_lava            = minetest.get_content_id("default:lava_source")
local c_nlava           = minetest.get_content_id("lbrim:lava_source")
local c_lavaflow        = minetest.get_content_id("default:lava_flowing")
local c_obsidian        = minetest.get_content_id("default:obsidian")
local c_vine            = minetest.get_content_id("nethervine:vine")
local c_bedrock         = minetest.get_content_id("bedrock:bedrock")

-- Externally located tables for performance.
local data = {}
local noisemap1 = {}
local noisemap2 = {}
local noisemap3 = {}
local noisemap4 = {}
local noisemap5 = {}

--[[
Notes on mapgen function. IMPORTANT!

The code loops through all positions in the mapchunk being generated *twice*, once to generate the nether,
and the second time to repair problems at chunk borders caused by caves overgenerating in the C++ mapgen.
These two loops work together, and must be understood together, since the loop which overgenerates can touch
chunks previously generated by the first 'normal' loop.

This 'hack' would not be necessary if we were using Singlenode for the C++ mapgen.
However, we're using Valleys, so the Lua mapgen must work nicely with it.
--]]

nethermapgen.generate_realm = function(minp, maxp, seed)
  local nstart = nethermapgen.NETHER_START
  local bstart = nethermapgen.BRIMSTONE_OCEAN
  local rstart = nethermapgen.BEDROCK_DEPTH

  -- Don't run for out-of-bounds mapchunks.
  local mindepth = nstart + 100
  if minp.y > mindepth and maxp.y > mindepth then return end

  -- Grab the voxel manipulator.
  local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
  vm:get_data(data) -- Read current map data.
  
  local area = VoxelArea:new{MinEdge=emin, MaxEdge=emax}
  local area2 = VoxelArea:new{MinEdge=minp, MaxEdge=maxp}
  
  local pr = PseudoRandom(seed + 65)
  
  local x1 = maxp.x
  local y1 = maxp.y
  local z1 = maxp.z
  local x0 = minp.x
  local y0 = minp.y
  local z0 = minp.z
  
  -- Compute side lengths. 
  local side_len_x = ((x1-x0)+1)
  local side_len_y = ((y1-y0)+1)
  local side_len_z = ((z1-z0)+1)
  local sides3D = {x=side_len_x, y=side_len_y, z=side_len_z}
  local sides2D = {x=side_len_x, y=side_len_z}
  local bp3d = {x=x0, y=y0, z=z0}
  local bp2d = {x=x0, y=z0}
  
  -- Get noisemaps.
  local perlin1 = minetest.get_perlin_map(nethermapgen.noise1param2d, sides2D)
  perlin1:get2dMap_flat(bp2d, noisemap1)
  local perlin2 = minetest.get_perlin_map(nethermapgen.noise2param2d, sides2D)
  perlin2:get2dMap_flat(bp2d, noisemap2)
  local perlin3 = minetest.get_perlin_map(nethermapgen.noise3param2d, sides2D)
  perlin3:get2dMap_flat(bp2d, noisemap3)
  local perlin4 = minetest.get_perlin_map(nethermapgen.noise4param2d, sides2D)
  perlin4:get2dMap_flat(bp2d, noisemap4)
  local perlin5 = minetest.get_perlin_map(nethermapgen.noise5param3d, sides3D)
  perlin5:get3dMap_flat(bp3d, noisemap5)
  
  -- Localize commonly used functions.
  local floor = math.floor
  local ceil = math.ceil
  local abs = math.abs
  
  -- First mapgen pass.
  for z = z0, z1 do
    for x = x0, x1 do
      -- Get index into 2D noise arrays.
      local nx = (x-x0)
      local nz = (z-z0)
      local ni2 = (side_len_z*nz+nx)
      ni2 = ni2 + 1 -- Lua arrays start indexing at 1, not 0. Urrrrgh. >:(
          
      local n1 = noisemap1[ni2]
      local n2 = noisemap2[ni2]
      local n3 = noisemap3[ni2]
      local n4 = noisemap4[ni2]
      
      local rs_top = ceil(nstart+abs(n1)*64)
      local rs_bot = floor(nstart-abs(n1)*64)
      
      local lakecel = bstart + 30
      local lakelav = bstart
      local lakebed = bstart - 2
      local islandi = bstart - 2
      
      if n4 > -0.3 then
        if abs(n2) > 0.6 then
          islandi = bstart + 5
          islandi = islandi + pr:next(0, pr:next(1, 2))
          islandi = islandi + floor(n1*4)
          -- Create random holes.
          if pr:next(1, 100) == 1 then islandi = bstart - 2 end
        elseif abs(n2) > 0.5 then
          islandi = islandi + pr:next(3, 5)
        end
      end
      
      lakecel = lakecel - pr:next(0, 1+floor(abs(n3) * 3.5))
      lakecel = lakecel + floor(abs(n1) * 6)
      
      -- First pass through column.
      for y = y0, y1 do
        local vp = area:index(x, y, z)
        local vu = area:index(x, y+1, z)
        local vd = area:index(x, y-1, z)
      
        -- 3D noise.
        local np = area2:index(x, y, z)
        local n5 = noisemap5[np]
        
        if y <= rs_top then
          -- Get the type already generated at this position.
          local ip = data[vp]
          
          -- Using mapdata already generated by the C++ mapgen, convert regular nodes to nether types.
          if ip == c_cobble or ip == c_mossycobble then
            data[vp] = c_netherbrick
          elseif ip == c_cobblestair then
            data[vp] = c_netherstair
          elseif ip == c_water or ip == c_waterflow then
            data[vp] = c_lava
          elseif ip ~= c_air and ip ~= c_vine then -- Vines can cross chunk borders. Don't replace them.
            -- Generate rackstone layer between nether and underworld.
            if y >= rs_bot and y <= rs_top then
              data[vp] = c_mgrackstone
            elseif y < rs_bot then
              if abs(n5) < 0.015 then
                data[vp] = c_mgrackstone
              else
                data[vp] = c_mgredrack
              end
            else
              data[vp] = c_stone
            end
          end
          
          -- Generate the endless nether lava ocean, with islands.
          if y <= lakebed or y <= islandi then
            -- Fill in map below brimstone ocean & create islands.
            data[vp] = c_redrack
          elseif y <= lakelav then
            data[vp] = c_nlava -- Special lava for brimstone ocean.
          elseif y <= lakecel then
            -- Carve out horizontal cavern above brimstone ocean.
            data[vp] = c_air
          elseif ip == c_air and y > lakecel and y <= lakecel+5 then
            -- Fill in huge ceiling holes created when huge caves
            -- intersect with the brimstone ocean realm.
            data[vp] = c_whitestone
          end
        end -- If Y coord is below nether start.
      
      end -- For all in Y coordinates.
    end -- For all in X coordinates.
  end -- For all in Z coordinates.
  
  -- Second mapgen pass, for things that need overgenerating.
  local ex1 = emax.x
  local ey1 = emax.y
  local ez1 = emax.z
  local ex0 = emin.x
  local ey0 = emin.y
  local ez0 = emin.z
  
  for z = ez0, ez1 do
    for x = ex0, ex1 do
      for y = ey0, ey1 do
        -- Get voxelmap indice.
        local vp = area:index(x, y, z)
        local ip = data[vp]
        
        -- Transform dungeons (over)-generated by the C++ mapgen.
        -- Also remove water.
        if y <= nstart then
          if ip == c_cobble or ip == c_mossycobble then
            data[vp] = c_netherbrick
          elseif ip == c_cobblestair then
            data[vp] = c_netherstair
          elseif ip == c_water or ip == c_waterflow then
            data[vp] = c_lava
          end
        end
        
        -- Bedrock layer.
        if y <= rstart+pr:next(1,pr:next(2, 3)) then
          data[vp] = c_bedrock
        end
      end
    end
  end
  
  -- These tables will be filled with positions for decorations,
  -- to be placed after the voxel manipulator code finishes.
  local chnk_pos_flame = {}
  local chnk_pos_crystal = {}
  local chnk_pos_tree = {}
  local chnk_pos_shroom = {}
  local chnk_pos_vine = {}
	local chnk_pos_grass = {}
	local chnk_pos_flower = {}
  
  local is_netherock = function(ip)
    if ip == c_redrack or
       ip == c_rackstone or
       ip == c_mgredrack or
       ip == c_mgrackstone then
      return true
    else
      return false
    end
  end
  
  -- Final mapgen pass, for finding floors and ceilings.
  -- Note: this has to be a seperate pass because otherwise the code
  -- will find floors and ceilings where there aren't any. Sad but true. :(
  for x = x0, x1 do
    for z = z0, z1 do
      for y = y0, y1 do
        local vp = area:index(x, y, z)
        local vu = area:index(x, y+1, z)
        local vd = area:index(x, y-1, z)
        
        local ip = data[vp]
        local iu = data[vu]
        local id = data[vd]
        
        -- Found floor.
        if is_netherock(ip) and iu == c_air then
          if pr:next(0, 2000) == 0 then
            chnk_pos_flame[#chnk_pos_flame+1] = {x=x, y=y+1, z=z}
          elseif pr:next(0, 5000) == 0 then
            chnk_pos_tree[#chnk_pos_tree+1] = {x=x, y=y+1, z=z}
          elseif pr:next(0, 3000) == 0 then
            chnk_pos_shroom[#chnk_pos_shroom+1] = {x=x, y=y+1, z=z}
					elseif pr:next(0, 200) == 0 then
						chnk_pos_grass[#chnk_pos_grass+1] = {x=x, y=y+1, z=z}
					elseif pr:next(0, 400) == 0 and y > -30750 then
						chnk_pos_flower[#chnk_pos_flower+1] = {x=x, y=y+1, z=z}
          end
        end
        
        -- Found roof.
        if is_netherock(ip) and id == c_air then
          if pr:next(0, 4000) == 0 then
            chnk_pos_crystal[#chnk_pos_crystal+1] = {x=x, y=y-1, z=z}
          elseif pr:next(0, 10) == 0 then
            chnk_pos_vine[#chnk_pos_vine+1] = {x=x, y=y-1, z=z}
          end
        end
      end
    end
  end
  
  -- Finalize voxel manipulator.
  vm:set_data(data)
  minetest.generate_ores(vm, minp, maxp)
  vm:set_lighting({day=0, night=0})
  vm:calc_lighting()
  vm:update_liquids()
  vm:write_to_map()
  
  for k, v in ipairs(chnk_pos_flame) do
    nethermapgen.scatter_flames(v)
  end
  
  for k, v in ipairs(chnk_pos_tree) do
    local p = table.copy(v)
    p.y = p.y - 1
    set_node(p, {name="rackstone:dauthsand"})
    firetree.create_firetree({x=p.x, y=p.y+1, z=p.z})
  end
  
  for k, v in ipairs(chnk_pos_shroom) do
    local p = table.copy(v)
    p.y = p.y - 1
    set_node(p, {name="rackstone:dauthsand"})
    redshroom.create_shroom({x=p.x, y=p.y+1, z=p.z})
  end
  
  for k, v in ipairs(chnk_pos_crystal) do
    nethermapgen.place_crystal(v)
  end
  
  for k, v in ipairs(chnk_pos_vine) do
    local p = table.copy(v)
    local r = pr:next(2, 7)
    for i = 1, r, 1 do
      if get_node(p).name ~= "air" then
        break
      end
      set_node(p, {name="nethervine:vine"})
      p.y = p.y - 1
    end
  end

  for k, v in ipairs(chnk_pos_grass) do
		-- Use swap_node to avoid triggering the construction timer.
		swap_node(v, {name="nether:grass_" .. math_random(1, 3)})
  end

  for k, v in ipairs(chnk_pos_flower) do
		-- Use swap_node to avoid triggering the construction timer.
		swap_node(v, {name="nether:glowflower"})
  end
end
